Field of the Invention
The present disclosure relates to a photodiode, which includes a graphene-silicon quantum dot hybrid structure, having improved optical and electrical characteristics by controlling the sizes of silicon quantum dots and the doping concentration of graphene, and a method of manufacturing the same.
Description of the Related Art
Graphene, which has superior optical performance as well as high electrical conductivity, has been increasingly utilized in next-generation displays, such as flexible displays and touch panels, in energy industry fields such as solar cells, in various electronics, such as smart windows, RFIDs, and the like.
Over the past several years, graphene has attracted considerable attention due to potential thereof for the growth of industrial technology as well as the development of basic science. In particular, a technique of manufacturing large-area graphene was recently developed, whereby application possibility thereof is increasing.
Among large-area graphene products, graphene manufactured by chemical vapor deposition (CVD), which is widely used in the industry, has a large area and high transmittance and electrical conductivity, thereby being expected to be applied to transparent electrodes.
To utilize graphene in optical and electronic devices, it is necessary to realize a diode structure which is a basic structure of a semiconductor device. In particular, if graphene is developed as a device having a hybrid structure with a silicon-based material widely used in the current industry, the ripple effect will be Very great compared to other materials.
Photodetecting devices or optical sensors, which are photoelectric conversion sensors that convert electromagnetic waves, such as light, into electrical signals, are utilized in various fields such as image sensing, communication, chemical/medical/biological sensing, and aerospace.
A representative material forming the basis of such photodetector devices is silicon Commercial silicon-based photodetector devices can detect light in the ultraviolet, visible, and infrared regions, respectively. Conventional photodetector devices have a limited light detection band, low photoresponsivity, and a low band gap energy of Si, and thus, generate heat under relatively high light energy (from ultraviolet light to visible light region energy), thereby having a problem in that the lifetime of devices is shortened.
Accordingly, research into development of a photodetector device using materials having a large energy bandgap to minimize heat generation due to absorption of light in the ultraviolet and visible ray regions is actively underway.
Especially, if the energy bandgap of silicon, which is the most important material in the industry at present, can be controlled, ripple effect thereof will be enormous. Especially, the quantum confinement effect (QCE) of silicon quantum dots should enable further increased light absorptivity and luminous efficiency in the short wavelength region, compared to bulk single-crystalline silicon (Si). Accordingly, silicon has attracted attention as one of very attractive materials of next-generation optoelectronic devices.
In addition, it is anticipated that very thin and flexible optoelectronic devices will be required in the future, and thus, research thereinto is actively carried out in the industry, academia and industry. In order to realize this, a transparent and flexible substrate should be used. However, since such a substrate is vulnerable to heat, graphene growing at a high temperature may be an alternative.
Further, even if growth is possible at high temperature, the process is complex and high costs caused therefrom are thus unavoidable, whereby there are many restrictions on commercialization.
Accordingly, there is need for a suitable material for next-generation photodetector devices and a structure thereof which allow a simple manufacturing process, easy fabrication of a transparent and flexible substrate, and exhibition of superior performances such as broadband, high sensitivity, and high detectability.
Until recently, research into photodetector devices based on colloidal quantum dots, such as CdS, CdSe, and PbS, which have superior performance in the visible region, have been reported. Colloidal quantum dot-based photodetector devices have advantages such as a simple fabrication process, low cost, and good sensitivity.
However, colloidal quantum dot-based photodetector devices have disadvantages such as a high operating voltage of 40 to 500V and a slow operating speed. Above all, use of Pb or Cd based materials is limited according to RoHS (Restriction of Specific Hazardous Substances), which took effect from Jul. 1, 2006.
Therefore, it is necessary to design and manufacture a photodetector device with a new structure or to develop a new material for photodetector devices to address the aforementioned problems of conventional photodetector devices.
Recently, research on photodetectors having various new materials and structures have been reported, but there is difficulty in commercializing the same due to low photoresponsivity and detectivity and driving at a relatively high voltage thereof.
Further, several photodetector devices, which have been reported to have superior performance, have a complex manufacturing process and there is a difficulty in manufacturing the same to have a large area.